Flying disc

ABSTRACT

An improvement to a flying disc that returns to the user by means of a string using rotational energy in a manner of a yo-yo. The flying disc has a lower wing  1  that generates a lift, a smaller wing  2  and an axle  3 . Between the wings  1,2  is a string  4  attached to the axle. The flying disc has at least one circular airfoil  11  and there are openings inside the area bound by its inner edge and the axle  3 . Air currents from the direction of the flight that pass over and under the airfoil  11  are able to effectively mix through these openings. When slung with the string  4 , the flying disc starts to rotate rapidly and flies away. It returns to the user when winding the string  4  back in the manner of a yo-yo.

PRIOR APPLICATIONS

This is a US national phase patent application that claims priority fromPCT/FI01/00569, filed Jun. 15, 2001, that claims priority from FinnishPatent Application No. 20001505, filed Jun. 22, 2000.

FIELD OF THE INVENTION

This invention is an improvement to a flying disc which returns to theuser by means of a string or corresponding elongated part, and usesrotational energy for the return flight in a way that resembles yo-yomotion. It may be used as a toy, for recreational purposes and assporting equipment.

BACKGROUND AND SUMMARY OF THE INVENTION

The device known as a yo-yo exemplifies some of the existing technologythat precedes the present invention. A yo-yo returns to the user bymeans of a string that first winds out and then in around an axle. Thestring forces the falling yo-yo to rotate and the primary source of thisrotational energy is gravitational potential energy that is convertedinto rotational kinetic energy. The essential directions of its basictranslational motion are vertical. It does not glide supported by air.Due to these characteristics the length of the yo-yo string is about0.5-1 metre.

A traditional saucer-shaped flying disc is represented, for example, inU.S. Pat. No. 3,359,678, Headrick et al. This device rotates around itsupright axis during translational flight generating lift. A great numberof different forms of flying disc have been developed from the basicidea and many of these have been patented. It is appropriate to referhere to a ring-shaped flying disc represented, for example, in U.S. Pat.No. 4,560,358, and consisting of a ring-shaped airfoil with an uncoveredinner area. These ring-shaped flying discs are somewhat more closelyrelated to this invention than the traditional discs, in that thesolutions to the problems of realising proper aerodynamic lift and lowair-resistance are somewhat similar to the present invention. Thetraditional flying disc and its further developed versions are usuallyused by several people, who throw the disc to one another. Otherwise thelone user has to follow the disc and retrieve it each time after it haslanded.

Goals and problems that somewhat more closely resemble those of thepresent invention, are sought and resolved in U.S. Pat. No. 3,802,117 byEngelhardt, and in patent publication WO 92/11913 by Tomberlin. A deviceaccording to Engelhardt's patent in its basic form consists asaucer-shaped flying disc, beneath which is a reel attached to a string.The user end of the string is fastened to a wand. The purpose of thedevice is to reel back to the person using it by means of the string. Asthe reel is positioned beneath the device and at a distance that isrelatively remote from its centre of gravity, the device tends to diveor climb at steep angles when the string tightens during flight and theflight then fails. For this reason it is difficult to make the devicerotate and move fast enough. The solution proposed in the publicationfor achieving flight stability is an additional weight added to thelower end of the reel, but this added weight actually creates newproblems. A flying toy according to Tomberlin's publication has twoidentical rotary elements joined by an axle. The rotary elements arefurnished with wings that create lift when the device rotates. Thisdevice creates lift expressly and exclusively by this rotary motionaround its vertical axis. After each cast it has to be turned upsidedown so that the airfoil-wings are in a position to generate lift.

While the devices here described attempt at least partially to solve thesame problems, they differ considerably from the present invention inrespect of their solutions. A type of flying disc that is more of astarting point for the present invention and its improvements isrepresented in Finnish patent no. 93426, throw and fly device by Kaisioand Kukkonen. A flying disc according to this patent consists of aconvexo-concave base-part resembling a traditional flying disc with atop-mounted flange at the end of a short axle. There is a space for thestring between the flange and the base-part. This space is about as wideas the diameter of the string. The device flies supported by air androtates around its vertical axis. The energy conserved in rotary motionreturns the device to its user by means of a string in a way thatresembles the function of the yo-yo.

An important problem of devices configured according to Pat. No. 93426FI is caused by this very narrow space for the string, which is only thediameter of the string or at most 1-2 diameters. This leads to asituation where the length of string for a single winding around theaxle changes considerably during flight. This means that the angularmomentum of the device decreases as it approaches its user. At the sametime kinetic energy of rotation is also consumed in correcting theflight path and in overcoming air-resistance. The flight speed thereforedecreases and there is a practical problem that flight often stallsbefore the return is complete. Another trouble is that the string tendsto tangle into the proposed narrow space in a way that is oftendifficult to disentangle and quite frustrating to the user.

Considerable improvements are achieved by a flying disc configuredaccording to the present invention. In particular, the air-resistance islower and the aerodynamic properties are more favourable than those ofPat. no. 93426 FI and other predecessors. The invention is based on thefact that air-currents flowing over and under the translationally movingcircular airfoil that forms part of this yo-yo returning flying disc,are able to mix through openings in the area bounded by the inner edgeof the circular airfoil and the axle. The present invention constitutesa breakthrough for more balanced flight and lower air-resistance. Thesehave hitherto remained major problems in all known solutions for flyingdiscs employing some kind of string arrangement and yo-yo function.There are also other benefits.

A yo-yo returning flying disc configured according to the presentinvention can be constructed to be lighter in proportion to theaerodynamic lift which it generates. This enables it to glide at lowertranslational speeds. It returns more easily than its predecessors onlonger strings. The improved flight properties also make it easier for abeginner to fly the device with a relatively short string. Improvedaerodynamic properties also make its flight more stable in windyconditions.

Using a slinging technique and a lighter construction according to thepresent invention the flying disc may be accelerated to a considerablyfaster rate of rotation. In this rotation the kinetic energy increasesin direct proportion to the square of the speed. It may thus beconsidered capable of storing more energy in the form of rotationalmovement than earlier versions. This increased rotational kinetic energyprovides enhanced stability at the turning point where the string tugson the flying disc and it reverses its direction of flight. The locationof the string vertically close to the centre of gravity also favourablyinfluences stability of the flying disc at this turning point.

One further benefit of the lighter construction is that the impact ofthe flying disc is reduced in the event that it accidentally collideswith the user. The user may be relaxed about flying the device and neednot worry about being hit by some rapidly flying heavy object if hefails to catch it.

Compared to current technology a construction according to the presentinvention brings about these and certain other improvements. The presentinvention is characterised by the claims appended hereto.

BRIEF DESCRIPTION OF DRAWINGS

The following description refers to the accompanying illustrations, inwhich:

FIG. 1 is a top view of one possible embodiment of the presentinvention.

FIG. 2 is a cross-sectional transverse view along the line A—A of theembodiment illustrated in FIG. 1 without the string.

FIG. 3 is the embodiment illustrated in FIGS. 1 and 2, which has beendismembered with the parts—the upper and lower wing—viewed from below atan oblique angle.

FIG. 4 is a side view of the embodiment illustrated in FIGS. 1, 2 and 3without the string.

DETAILED DESCRIPTION

In FIGS. 1 and 2 there is a flying disc constructed according to thepresent invention, which includes a lower wing (1) and an upper wing (2)with a space between these for a string (4) to be wound. The term“string” is used here in a broad sense to include any elongated part offlexible material, for example strings, braids, bands, cords and lines.The string (4) is attached with a loosely-fitting loop around the axle(3) that is formed by centre hub area (13) of the lower wing (1) and thecentre hub area (23) of the upper wing (2). The string (4) may also beattached by some other method or means with the purpose of remainingattached during the entire flight. A loosely-fitting loop is beneficialin that it allows the rotating movement to continue smoothly at theturning point without interruption. It is emphasised that the width offree space for winding the string (4) is significantly greater than thediameter of the string that is used. In the illustrated embodiment it isof the order of 5-20 times this diameter, depending on the string thatis used. Therefore the angular momentum of the flying disc and thelength of string per single revolution is sufficiently uniform forpractical purposes throughout the entire flight-path.

In this embodiment the length of the string (4) is usually of the orderof 3 to 20 meters. A thinner string is chosen for greater lengths. Tofly a flying disc according to the present invention the string (4) iswound around the axle-arrangement (3) described. The other end of thestring (4) is usually attached to the user's right hand forefinger by aloop or some other means, or to the left hand forefinger if the user isleft-handed. It may also be attached, for example, to some other fingeror to the wrist. The flying disc is held in the hand and raised to astarting position—usually level with the horizontal. The grip isreleased and then immediately, before the disc has time to fall, the armis accelerated in a brisk swing away from the flying disc. The spoolformed by the lower wing (1) and the upper wing (2) is accelerated intoa rapid rotation by the string (4) pulling it. At the same time thedevice slings into flight. When the string has entirely unwound theflying disc reverses its direction of flight and starts to return. Thestring (4) stretches somewhat, opposing the translational motion, andthe disc reverses its direction smoothly. The speed of translationalmotion is essentially maintained when the direction is reversed. At thesame time the flying disc continues its rapid rotation and therefore thestring (4) now winds back in around the axle (3) and the disc speedsback to the user. When it comes close the user can catch it. After asuccessful flight the device is immediately ready to be slung for a newflight in the manner described above.

FIG. 3 illustrates the lower wing (1) and the upper wing (2) apartbefore they are fastened together. It may also be possible tomanufacture these wings for a flying disc according to the presentinvention as a single piece, or the wings may also naturally beconstructed with more than two pieces. In this illustrated embodimentfastening aids can be seen on the central hub area (23) of the upperwing (2). These fit into forms of the central hub area (13) of the lowerwing (1), which facilitate the fastening with a so-called snap-fitmethod. In this method the parts are fastened by pressing them togetherso that the convenient forms interlock. An upright cylindrical surface(14) of the central area (13) of the lower wing (1) and thecorresponding upright cylindrical surface (24) of the upper wing (2)enable easier adjustment of the parts when they are assembled. Theseforms are also related to the injection moulding process used inmanufacturing the parts. The lower wing (1) and the upper wing (2) areinjection moulded in a suitable thermoplastic such as polypropylene.Other materials and manufacturing methods may also be applied withoutdeparting from the spirit of the invention.

With the present invention an aerodynamically favourable effect isachieved by forming openings in the surfaces of the disc that arepositioned according to the invention. In the embodiment described thereare openings not only on the lower wing (1), but also on the upper wing(2). The aerodynamic effect of these openings is further described inthe following paragraphs. One subsidiary advantage of these openings isto enable a reduction in the weight of the construction. This derivesfrom the fact that traditional injection moulding technology imposeslimits on the minimum thickness of plastic parts. In this method the hotthermoplastic is injected in liquid form into a metal mould and thensolidified at lower temperature. The thickness of the wings (1) and (2)must exceed about 1 millimetre because in practice plastic material inliquid form does not flow in channels that are too narrow. Thus withincertain limits the minimum weight of the parts depends quite directly inpractice on the surface area.

The lower wing (1) includes a circular airfoil (11) that encircles itsvertical axis. The cross section of the airfoil (11) bends in a curve,thereby generating upward lift in the same way as an aeroplane wing whenmoving translationally through the air. Air currents pass faster overthe airfoil than below it, and the resulting difference in air pressuregenerates the lift. As shown in FIG. 2 the upper surface of the airfoil(11), that is cross sectioned toward the vertical axis of the flyingdisc, starts from the lowest level and bends upwards following asomewhat circular path before sloping down to lower level following aline that is tangential to the said circle. This line is at a 15° angleto a line perpendicular to the vertical axis of the flying disc. Atessentially the lowest level of the flying disc one of the wing spokes(12) can be seen connected to the circular airfoil (11). The materialthickness over the entire profile is quite uniform in this embodimentthat is adapted for manufacture by injection moulding. Naturally withoutdeparting the scope of this invention the airfoil (11) could bemanufactured in many different ways and of many possible materials. Forexample it could be made of foam plastic and the material thickness ofthe profile could vary at different distances from the vertical axis.Many shapes of profile in addition to those described can be applied,having regard to the laws of aerodynamics. The wing spokes (12) connectthe circular airfoil (11) to the central hub area (13). In the depictedembodiment there are three wing spokes (12). The airfoil (11) is theonly significant lift-producing element in the lower wing (1). Aconsiderable part of the area between inner limits of the airfoil (11)and the vertical axis is open to air currents, in other words there areopenings between the wing spokes (12). In the depicted embodiment thesecomprise about 75 percent of the total area described. These openingsenabling free airflow through the lower wing (1) are of the utmostimportance, as they enable the air currents passing over and under theairfoil (11) to meet and mix within the area of the airfoil (11), whichconsiderably balances and enhances flight performance. It worthrepeating that besides this, such a use of openings also considerablyreduces the surface area needed to generate a certain lift effect.

The upper surface of the circular airfoil (21) of the upper wing (2),that is cross sectioned toward the vertical axis in the embodimentdepicted, first follows a circular path and then near the inner edgeslants steeply upwards in the circle fold (25) of the airfoil (21). Theslanting surface extends up to more or less the greatest height level ofthe upper surface of the circular airfoil (21), and is joined to theupper wing hub area (23) by means of three wing spokes (22). The circlefold (25) prevents the string (4) from getting tangled in the wingspokes (22). This generates some negative lift in translationalmovement. In the depicted embodiment of the present invention thecircular airfoil (11) of the lower wing (1) generates the main lift forthe flying disc.

By a construction according to the present invention the axle (3) andthe upper wing (2) may be fitted into the hollow inner area of the lowerwing (1) so that in the transverse view of this particular embodimentshown in FIG. 4 the upper wing (2) is vertically entirely between theuppermost and lowermost points of the airfoil (11). In other words it ishidden from view behind the profile of the circular airfoil (11).

It should be noted that within the scope of this invention but differingfrom the depicted embodiment, the upper wing (2) may well be constructedwith small openings or with no openings at all. It is quite sufficientfor the purpose of this invention that there is enough open surface inthe inner area of the circular airfoil (11) of the lower wing (1) toenable the air currents passing over and under the airfoil (11) to mixeffectively through these openings. Compared to the current technologyof flying discs that return with a yo-yo like function, the presentinvention considerably reduces air-resistance and achieves abreakthrough both in glide-performance and in flight-stability.

It must be understood that the invention is capable of considerablevariation and modification without departing from the spirit of theinvention. We therefore do not wish to be restricted to the precisedetails of the constructions set out herein, but desire to availourselves of such modifications as fall within the scope of the appendedclaims.

I claim:
 1. A returning flying disc comprising a lower wing [1], anupper wing [2] of smaller diameter mounted axially, and between these anaxle [3] connecting the wings perpendicularly with a clearance betweenthem, and a string [4] or corresponding part that is attached to theaxle [3] and that can wind around this axle so that when allowed to flythe flying disc returns as the string winds back into a free spacebetween the wings, characterized in that the lower wing [1] has at leastone circular airfoil [11] generating lift on horizontal flight, and thatthere are openings within an area bounded by an inner edge of thecircular airfoil [11] and the axle [3], so that the air-currents from adirection of flight that pass over and under the airfoil [11] are ableto mix through these openings, axle (3) being disposed below anuppermost point (11 a) of the airfoil (11).
 2. A flying disc accordingto claim 1, characterized in that the upper wing [2] and the axle [3],when viewed from a side, lie substantially between planes that areprojected by revolving around a vertical axis those lines perpendicularto it that pass through a uppermost and the lowermost points of theairfoil [11].
 3. A returning flying disc comprising a lower wing [1], anupper wing [2] of smaller diameter mounted axially, and between these anaxle [3] connecting the wings perpendicularly with a clearance betweenthem, and a string [4] or corresponding part that is attached to theaxle [3] and that can wind around this axle so that when allowed to flythe flying disc returns as the string winds back into a free spacebetween the wings, characterized in that the lower wing [1] has at leastone circular airfoil [11] generating lift on horizontal flight, and thatthere are openings within an area bounded by an inner edge of thecircular airfoil [11] and the axle [3], so that air-currents from thedirection of flight that pass over and under the airfoil [11] are ableto mix through these openings the upper wing [2] having at least onecircular airfoil [21], and that there are openings within the areabounded by the inner edge of the circular airfoil [21] and the axle [3],so that air-currents from the direction of flight that pass over andunder the airfoil [21] are able to mix through these openings.
 4. Aflying disc according to claim 1, characterized in that the airfoil [11]of the lower wing [1] is joined to the axle [3] by two or more wingspokes [12] with openings between them.
 5. A flying disc according toclaim 3, characterized in that the airfoil [21] of the upper wing [2] isjoined to the axle [3] by two or more wing spokes [22] with openingsbetween them.
 6. A flying disc according to claim 5, characterized inthat the wing spokes [12] and [22] bend in a curve towards hub areas[13] and [23], and that parts of the said spokes that are nearest to avertical axis of the flying disc and the hub areas [13] and [23] formthe axle [3].
 7. A flying disc according to claim 1, characterized inthat the upper surface of hub area [13] of the lower wing [1] and thebottom surface of the hub area [23] of the upper wing [2] are mainjoining area of the said wings.
 8. A flying disc according to claim 1,characterized in that an area of the openings is at least 50% of thewhole area bounded by the inner edge of the circular airfoil [11] andthe axle [3].